The Congregation for Divine Worship and the Discipline of the Sacraments’ document Redemptionis Sacramentum, dated March 25, 2004, states the following (par. 154-156):
As has already been recalled, “the only minister who can confect the Sacrament of the Eucharist in persona Christi is a validly ordained Priest”. Hence the name “minister of the Eucharist” belongs properly to the Priest alone. Moreover, also by reason of their sacred Ordination, the ordinary ministers of Holy Communion are the Bishop, the Priest and the Deacon, to whom it belongs therefore to administer Holy Communion to the lay members of Christ’s faithful during the celebration of Mass. In this way their ministerial office in the Church is fully and accurately brought to light, and the sign value of the Sacrament is made complete.
In addition to the ordinary ministers there is the formally instituted acolyte, who by virtue of his institution is an extraordinary minister of Holy Communion even outside the celebration of Mass. If, moreover, reasons of real necessity prompt it, another lay member of Christ’s faithful may also be delegated by the diocesan Bishop, in accordance with the norm of law, for one occasion or for a specified time, and an appropriate formula of blessing may be used for the occasion. This act of appointment, however, does not necessarily take a liturgical form, nor, if it does take a liturgical form, should it resemble sacred Ordination in any way. Finally, in special cases of an unforeseen nature, permission can be given for a single occasion by the Priest who presides at the celebration of the Eucharist.
This function is to be understood strictly according to the name by which it is known, that is to say, that of extraordinary minister of Holy Communion, and not “special minister of Holy Communion” nor “extraordinary minister of the Eucharist” nor “special minister of the Eucharist”, by which names the meaning of this function is unnecessarily and improperly broadened.